The present invention relates to printing equipment and is concerned more particularly with equipment for line printing along a continuously moving web of sheet material at regularly spaced intervals.
In many packaging operations, a web of sheet material is cut in sections which are utilized as the wrappers or labels on the exterior of sealed packages. Frequently it is desirable to place identifying codes or other information on the wrapper but such information must be printed on the web during the wrapping or labeling operation. For example, lot numbers or date codes on packages containing food stuffs and other perishable materials determine when the products were packaged or when the contents will no longer be suitable for consumption or use. It is usually not possible to determine in advance when a particular label or wrapper will be applied to a package and therefore, pre-printing the labels with the identifying codes is not feasible.
For these reasons code dating equipment is employed within a packaging machine and frequently operates on a moving web of wrapping material as the web is drawn through the machine and applied to packages during wrapping or labeling operations. One such dater is disclosed in co-pending application Ser. No. 607,665 entitled HIGH SPEED PRINTER and filed on Aug. 25, 1975 by Lawrence W. Schoppee. The coder dater in the co-pending application utilizes a series of web guiding rollers at the printing station which rollers are operated in synchronism by a cyclic drive mechanism. In certain packaging machines, a less complex printing mechanism is desired.
It is, accordingly, a general object of the present invention to provide a simplified apparatus for printing information cyclically on a web of moving sheet material as the web advances through a machine at a printing station.